Steadily increasing demands for productivity and performance placed on agricultural machines and implements, especially soil tilling implements and combined cultivating and sowing machines, is resulting in larger machines. These include soil tilling implements and cultivating machines such as ploughs, harrows, cultivators, rotary hoes and planters, sowing machines and drilling machines, or cultivating and sowing machines which are a combination of two or more of the aforementioned implements. The increasing geometric dimensions of these machines and implements in turn lead to an increase in the weight. The resulting increased pressure exerted on the soil by the wheels increases compaction of the soil, which may have a negative effect on soil cultivation and tilling.
One possible way of reducing compaction is to distribute the weight of the machine or the implement over a larger soil contact area. Typically this is achieved by distributing load to two wheels rather than one to thereby create a larger contact area. Machines and implements fitted with two-wheel arrangements therefore exert a lesser soil pressure than similar machines and implements with single-wheel arrangements. Less soil pressure and compaction has a positive effect on soil cultivation and tilling. Axle suspensions with two wheel axles rigidly connected together are used to transmit loads evenly to both wheels.
Such two-wheel arrangements are disclosed in EP 1179289 A2, for example, wherein an attachment frame for soil tilling implements is provided with two-wheel arrangements. Each wheel arrangement includes an axle suspension with a wheel axle that extends on both sides of an axle suspension housing. The wheel axles are rigidly connected relative to one another so the weight of the frame and the implement acting on the wheel arrangement is distributed to both wheel axles and to the wheels. The fact that the wheel axles are rigidly connected to one another has a disadvantageous effect since the wheels cannot move independently of one another in a vertical direction, and in certain situations the weight cannot be optimally distributed. If one of the wheels is raised by an elevation or irregularity in the ground, the second wheel is also raised and lifted from full soil contact. If just one of the wheels encounters a depression in the ground, the second wheel keeps the first wheel out of ground contact. Similar effects occur when the soil tilling implement is used on inclines.